package map;

import bst.Bst;

public class BSTMap<K extends Comparable<K>,V> implements Map<K,V>{

    private class Node{
        public K key;
        public V value;
        public Node left,right;

        public Node(K key,V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    //向二分搜索树中插入元素(key,value)
    public void add(K key, V value) {
        root = add(root,key,value);
    }

    //向以node为根的二分搜索树中插入元素key,value，递归实现
    //返回插入新节点的二分搜索树的根
    private Node add(Node node,K key, V value){
        if(node == null){
            size ++;
            return new Node(key,value);
        }
        if(key.compareTo(node.key) < 0){
            node.left = add(node.left,key,value);
        }else if(key.compareTo(node.key) > 0){
            node.right = add(node.right,key,value);
        }else{
            node.value = value;
        }
        return node;
    }



    public V remove(K key) {
        Node node = getNode(root,key);
        if(node != null){
            root = remove(root,key);
            return node.value;
        }

        return null;
    }


    //删除以Node为根的二分搜索树中键为key的节点，递归算法
    //返回删除节点后新的二分搜索树的根
    private Node remove(Node node ,K key){
        if(node == null){
            return null;
        }
        if(key.compareTo(node.key) < 0){
            node.left = remove(node.left,key);
            return node;
        }else if(key.compareTo(node.key) > 0){
            node.right = remove(node.right,key);
            return node;
        }else{ //e == node.e`
            //待删除节点左子树为空的情况
            if(node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            if(node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size --;
                return leftNode;
            }

            //待删除的节点左右字树均不为空的情况
            //找到比待删除节点大的最小节点，即待删除几点的右子树的最小节点
            //用这个节点替待待删除节点的位置
            Node successor = minimum(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;
            node.left = node.right = null;
            return successor;
        }
    }

    //删除以node为根的二分搜索树中的最小节点
    //返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node){
        if(node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size --;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    private Node minimum(Node node){
        if(node.left == null){
            return node;
        }
        return minimum(node.left);
    }

    public boolean contains(K key) {
        return getNode(root,key) !=null;
    }

    public V get(K key) {
        Node node = getNode(root,key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue) {
        Node node = getNode(root,key);
        if(node == null){
            throw new IllegalArgumentException("does not exisit");
        }
        node.value = newValue;
    }




    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    //返回以node为根结点的二分搜索树key所在节点
    private Node getNode(Node node,K key){
        if(node == null){
            return null;
        }
        if(key.compareTo(node.key) == 0){
            return node;
        }else if(key.compareTo(node.key) < 0){
            return node;
        }else {
            return getNode(node.right,key);
        }

    }


}
